The present invention relates to valve fittings in general, and more particularly to a self-closing valve fitting.
There are already known self-closing valve fittings in which a housing bounds an internal space and includes a water inlet and a water outlet which communicate with the internal space and a valve seat situated between the water inlet and the water outlet, and in which a valve piston is received in the internal space of the housing for movement toward and away from the valve seat and for attendant cooperation with the valve seat. The valve piston then delimits in the internal space, at its side which faces away from the valve seat, a relief chamber. In such known self-closing valve fittings, an actuation valve is arranged in the valve piston between the relief chamber and the water outlet and forms a part of an arrangement for self-retention of the fitting during a delayed opening movement of the valve piston.
In the self-closing valve fittings of this kind, air is naturally initially present in the self-closing valve fitting and especially also in the relief chamber during the first use of such fitting after its installation. Experience has shown that, in the self-closing valve fittings of the type here under consideration, because of the presence of the actuation valve which is built-in into the valve piston, there is not achieved a sufficient escape of the air contained in the relief chamber to the water outlet under certain circumstances, especially when such self-closing valve fitting is installed in a horizontal position. This is so because then a not inconsiderable air cushion is possibly collected at the upwardly situated region of the jacket wall bounding the relief chamber, without being able to escape from the relief chamber to the water outlet. However, such an air cushion remaining in the relief chamber can cause such an elastic behavior of the pressurized medium which is present in the relief chamber and which is constituted by the air cushion and the water, that an excessively wide opening of the valve piston occurs at the switching-on time. As a result of this, the self-holding action of the self-closing valve fitting can break down, since it is mechanically or hydraulically designed. Then, the actuation valve closes immediately and the valve piston also immediately returns into its position in which it engages its associated valve seat. This, of course, is very disadvantageous since it defeats the very purpose of the valve fitting.